The seed phrase is a single, central, core secret. And then, using math—the math is actually called Bip44—what you can do is you can run math on that seed phrase to generate you an account ... An Ethereum account is an address a public key and a private key. So, account 1 has an address, public key, private key. Account 2 has an address, public key, private key. And you can generate as many of those as you like.